Optimize layer clears.
Optimize layer clears.

Don't clear the entire texture when we use textures that are bigger
than the layer itself. This will save time during the glClear() calls.

Change-Id: I06f3259ba62affb3708ba69ea41418832c7e1a65

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base